44 



The early Tertiary Rodents known from South America are 

 the genera Megamys, Theridromys, and a large species referred 

 to Arvicola. In Brazil, the Pliocene Rodents found are referred 

 to the existing genera Cavia, Kerodon, Lagostomus, Ctenomys, 

 Hesperomys, Oxymycterus, Arvicola and Lepus. A new genus, 

 Cardiodus, described from this horizon, is a true Rodent, but 

 the peculiar Typotherium, which has been referred to this order 

 by some authorities, has perhaps other affinities. In the' 

 Post-Tertiary, the Rodents were very abundant in South 

 America, as they are at present. The species are in most 

 instances distinct from those now living, but the genera are 

 nearly the same. The Caviidae were especially numerous. 

 Cercolabes, Myopolamus, and Lagostomus are also found, and two 

 extinct genera, Phyllomys and Lonchophorus, 



The Cheiroptera, or Bats, have not been found in this country 

 below the middle Eocene, where two extinct genera, Nyctilestes 

 and Nyclitherium, are each represented by numerous remains. 

 These fossils all belong to small animals, and, so far as they 

 have been investigated, show no characters of more than generic 

 importance to distinguish them from the Bats of to-day. No 

 other members of this group are known from our Tertiary. 

 In the Post-Tertiary, no extinct species of Bats have been 

 found in North America, but from the caves of Brazil quite 

 a number have been reported. These all belong to genera 

 still living in South America, and most of them to the family 

 Phyllostomidcz. 



The Insectivores date back, in this country, at least to the 

 middle Eocene. Here numerous remains occur, which have 

 been described as belonging to this order, although it is pos- 

 sible that some of them were insect-eating Marsupials. The 

 best known genera are, Hemiaeodon, Centetodon, Talpavus, and 

 Entomacodon ; all represented by animals of small size. In 

 the Miocene, the bones of Insectivores are comparatively abun- 

 dant, and the genera best determined are Ictops and Leptictis. 

 A few specimens only have been found in the Pliocene and 

 Post-Plioeene, most of them related to the Moles. No extinct 



